The enzyme chymase, which is mentioned simply as chymase sometime hereinafter, is a chymotripsin-like serine protease. Chymase is mainly stored in mast cells and can be secreted in tissues of heart, blood vessel, skin and others. As one of the main actions of chymase, it is known that chymase has such action as to produce angiotensin II from angiotensin I which is a substrate. Angiotensin II is known to exhibit a strong constrictive activity on vascular smooth muscle cells, leading to hypertension and cardiac insufficiency. It has hitherto been thought that the production of angiotensin II is affected mainly by the participation and action of angiotensin-converting enzyme (ACE).
Recently, however, there has been suggested newly that another physiological mechanism exists for the production of angiotensin II in local tissues as induced by serine proteinase, which is different from that by ACE. Reference is made specifically to some reports which reveal that angiotensin II as produced in human heart and blood vessel systems is mainly resulted from the conversion of angiotensin I by a chymase rather than the conversion of angiotensin I by ACE [see “Biochem. Biophys. Res. Coummun.”, 1987, No.149, p.1186; and “Circ. Res.”, 1990, No.66, p.883]. Other literatures have reported that chymase has many functions, including promotion of the degranulation of mast cell, activation of interleukin-1β, conversion of endoserine, and so on.
In view of these facts, it is expected that a compound capable of inhibiting the enzymatic activity of a human chymase, that is, a human chymase inhibitor is useful as new medicines for the therapeutic or prophylactic treatment of diseases in the cardiovascular system, such as hypertension, cardiac insufficiency, and of allergic diseases such as asthma, rheumatism, atopic dermatitis and others.
Until now, there are known several compounds having a chymase inhibitory activity. For example, we, the inventors of this invention, have already found that the cultivation of a microbial strain, SF2809 of a family Micromonosporaceae, which is a new microorganism as isolated by us from a soil sample collected at Hachijo Island, Tokyo, produces six compounds each having a chymase inhibitory activity in the resulting culture. Then, we have succeeded in isolating these six compounds from the culture and determined fully their chemical structures. As a result, we have recognized that all the six compounds are to be novel compounds hitherto unknown, and we have designated them as SF2809-I substance, SF2809-II substance, SF2809-III substance, SF2809-IV substance, SF2809-V substance and SF2809-VI substance, respectively. These SF2809-I, -II, -III, -IV, -V and -VI substances each are compounds which are represented by the following formula (A), formula (B), formula (C), formula (D), formula (E) and formula (F). 
It has been confirmed that each of the substances SF2809-I, -II, -III, -IV, -V and -VI above-mentioned, as novel compounds, has a chymase inhibitory activity (refer to the specification of PCT application No. PCT/JP99/06738 filed on Dec. 1, 1999 and laid open under an international publication WO 00/32587 on Jun. 8, 2000).
On the other hand, there are disclosed peptide-type compounds having an inhibitory activity to human chymase in the specifications of the publications WO95/27053 and WO95/27055, and non-peptide-type chymase inhibitors in the specifications of the publication WO96/04248 and Japanese Patent Application publication Kokai Hei-10-87567. Furthermore, several chymase inhibitory compounds originated from a microorganism metabolite are disclosed in Japanese Patent Application publication Kokai Hei-10-101666. Up to now, however, these known compounds having a chymase inhibitory activity have not yet been utilized clinically in therapeutic and prophylactic treatments of the various diseases as above-mentioned in which a chymase can participate.
Thus, at present, there occurs a keen demand in the art to provide such new compounds which have a high chymase inhibitory activity with low toxicity against mammals.
While, the chemical structures of SF2809-I, -II, -III, -IV, -V and -VI substances of the formulae (A)-(F) given above, respectively, which have been provided by us, differ from those of the already known chymase inhibitors, and it has been expected that SF2809-I to IV substances are useful as chymase inhibitors usable for elucidation of the mechanism of the chymase inhibitory activity and also for studying the physiological activities other than the chymase inhibitory activity. However, SF2809-I to VI substances which are the metabolic products of a microorganism have such disadvantage that the steps of the process required for their isolation and purification are complicated when the SF2809-I to VI substances are to be isolated from their culture broth of the SF-2809-I to VI-producing microorganism. Another disadvantage is in that the amounts of SF2809-I to VI substances so produced by cultivation of said microorganisms are only very small.
Accordingly, so far as there is used the process for the production of SF2809-I to VI substances by a small scale cultivation of the SF2809 strain belonging to Micromonosporaceae as above-mentioned, there necessarily exists such problem that the amount produced of each of SF2809-I to VI substances is much poorer than the amount which will be required to be employed for carrying out further investigations on the progress of chemical syntheses for producing novel derivatives from the SF2809 substances in order to improve their physiological activities and also will be required to be employed for studying the utilizability of the SF2809 substances as a chymase-inhibitor.
It is now strongly demanded to develop and provide such new chemical synthetic processes for producing SF2809-I to VI substances, which can make it possible to produce each of SF2809 substances in ample amount and in an efficient way. However, there was no available chemical process in the prior art which can be utilized directly to develop new chemical synthetic process for producing the SF2809-I to VI substances.
We, the inventors of this invention, have made search in a lot of chemical literature, with our intention of finding out some chemical reactions which are utilizable to create and develop novel processes for chemical synthetic production of the SF2809-I to VI substances. According to this search, we have now found that, in respect of the processes for chemical synthesis of bis-indole derivatives having two indole groups bonded together via a methylene group, there is known a process of synthesizing a symmetric bis-indole derivative of the undermentioned formula (J) in which process two molecules of an indole compound of the undermentioned formula (G) are subjected to a condensation reaction with a benzaldehyde derivative of the undermentioned formula (H) according to the following reaction equation (A):Reaction Equation (A) wherein R stands for phenyl group, hydroxymethyl methyl group, formyl group, cyano group, acetyl group, or dimethylaminomethyl group [see Ulf Pindur, “Arch. Pharma.” (published from Weinheim), Vol.317, pp.502-505 (1984)].
There is also known a chemical synthetic process for producing a bis-quinol derivative having two 4-hydroxy-1-methyl-2-quinoline moieties bonded together via a methylene group, in which process two molecules of 4-hydroxy-1-methyl-2-quinoline of the undermentioned formula (K) are subjected to a condensation reaction with an imilidene compound of the undermentioned formula (L) so as to synthesize the symmetric bis-quinol derivative of the undermentioned formula (M), according to the following reaction equation (B): wherein R1 stands for methyl group or phenyl group and R2 stands for hydrogen atom, chlorine atom, methyl group, methoxy group or nitro group [see V Sudhakarrao and Malleshwar Daebarwar, “Indian Journal of Chemistry” Vol.25B, pp.540-541 (1986)].
Furthermore, there is known a chemical synthetic process for producing an indole derivative having an oxolane ring bonded to an indol-3-yl group via a methylene group, in which process an indole compound of the undermentioned formula (G′), paraformaldehyde of the formula (N) and an oxolane derivative of the formula (O) are simultaneously subjected to condensation reaction by a single step reaction of multicomponents so as to synthesize an indole derivative of the undermentioned formula (O), according to the following reaction equation (C): wherein R stands for a group selected from hydrogen atom, bromine atom, methyloxy group, cyano group and phthaliminomethyl group and X stands for an integer of 1 or higher [see “Synthesis” p.254 (1999)].
However, it is to be noticed that in this process, the 3-position of the indole compound of formula (G′) is the site of the reaction with the compound of formula (N), and so the 2-position of the indole ring of formula (G′) does not participate in the reaction as concerned, and that the yield of the compound of formula (Q) as produced in said single step reaction of the multicomponents is not so good.
We have once presumed that, with reference to the process of the reaction equation (A), the process of the reaction equation (B) and the process of the reaction equation (C) as subjected to our above examination, it would be difficult to foresee and predict any appropriately devised chemical process which can produce, through a chemical synthetic route, each of the SF2809-I to VI substances having the unique structures of the above-mentioned formulae (A) to (F).
On the other hand, in recent years, there has been developed noticeably “combinatorial chemistry” as a novel technique capable of speeding up the generation of lead compounds and the optimization of these lead compounds and capable of reducing the period of time required for searching prospective compounds usable for new medicines, in the field of the development of medicine [refer to “Molecular Diversity and Combinatorial Chemistry”, written by I. M. Chaikin and K. D. Janda, and published by American Chemical Society in 1996; and “J. Med. Chem.”, Vol.37, p.1233 (1994); and “Chem. Rev.”, Vol.96, p.555 (1996)]. One of the core techniques of “combinatorial chemistry” is a combinatorial synthesis in which a compound library comprising many compounds is prepared rapidly. In the process of combinatorial synthesis, there are included a solid phase synthesis wherein the synthesis of a compound is carried on an insoluble solid polymeric support, called as a solid phase, as well as a liquid phase synthesis wherein the synthesis of an aimed compound is carried out in a solution, which liquid phase synthesis has been used much prominently [see “A Practical Guide to Combinatorial Chemistry”, written by A. W. Czarnik and S. H. DeWitt, and published by American Chemical Society (1997)]. Among the known processes for the combinatorial liquid phase synthesis as mentioned above, a superior process is a multicomponent single step reaction procedure in which a compound is synthesized by reactions of multiple (3 or more) and different reaction component compounds in a single reaction step for rapid preparation of a compound library, resulting in a merit such that the library of compounds can be prepared much more speedily, as compared with such a synthetic method in which the multiple and different reaction component compounds are reacted successively in multi-reaction steps. As examples of the multicomponent single step reaction procedure, there are known Ugi reaction [see “Angew. Chem. Int. Ed. Engl.”, Vol.34, p.2280 (1995)] and Mannich-type reaction [see “Synthesis”, p.1401 (1999)].